Introduction and Structure of the pelvic walls pdf - Pelvis

Basic Anatomy

241

bones) anteriorly. Above the brim is the

The true pelvis has an inlet, an outlet, and a cavity.

bony canal through which the child passes during birth.

vis is of great importance for obstetrics, because it is the

Knowledge of the shape and dimensions of the female pel

True Pelvis

the true pelvis.

During the early stages of labor, it helps guide the fetus into

3rd month of pregnancy helps support the gravid uterus.

nal cavity. It supports the abdominal contents and after the

upper end and should be considered as part of the abdomi

the anterior abdominal wall. The false pelvis flares out at its

and the iliacus muscles, and in front by the lower part of

behind by the lumbar vertebrae, laterally by the iliac fossae

The false pelvis is of little clinical importance. It is bounded

sacrum is directed forward and downward.

faces upward and backward and the anterior surface of the

This means that the pelvic surface of the symphysis pubis

superior iliac spines should lie in the same vertical plane.

tion. The front of the symphysis pubis and the anterior

trunk, with the individual standing in the anatomic posi

the correct orientation of the bony pelvis relative to the

It is important for the student, at the outset, to understand

true pelvis

which forms part of the abdominal cavity. Below the brim

false pelvis,

is the

Orientation of the Pelvis

False Pelvis

C H A P T E R O B J E C T I V E S

■

The pelvis is a bowl-shaped bony structure that protects the ter-

minal parts of the gastrointestinal tract and the urinary system

and the male and female internal organs of reproduction.

■

It also contains important nerves, blood vessels, and lymphatic

tissues.

■

The purpose of this chapter is to review the significant anatomy

of the pelvic walls relative to clinical problems. Particular atten-

tion is paid to age and sexual differences and to the anatomic

features associated with pelvic examinations.

C H A P T E R O U T L I N E

(continued)

Radiographic Anatomy 259
Surface Anatomy 259

Surface Landmarks 259

Iliac Crest 259

Anterior Superior Iliac Spine 260

Posterior Superior Iliac Spine 260

Pubic Tubercle 260

Pubic Crest 260

Symphysis Pubis 260

Spinous Processes of Sacrum 260

Sacral Hiatus 260

Coccyx 260

Viscera 260

Urinary Bladder 260

Uterus 260

Rectal and Vaginal Examinations as

a Means of Palpating the Pelvic

Viscera 261

natomy

asic

The pelvis

(joint between bodies of pubic

symphysis pubis

ward around the inner surface of the ileum) laterally,

(a line that runs downward and for

iliopectineal lines

upper margin of the first sacral vertebra) behind, the

(anterior and

sacral promontory

which is formed by the

pelvic brim

The pelvis is divided into two parts by the

organs of reproduction.

parts of the intestinal and urinary tracts and the internal

basin-shaped structure that contains and protects the lower

. The bony pelvis thus forms a strong

sacroiliac joints

and posteriorly with the sacrum at

symphysis pubis

The two hip bones articulate with each other anteriorly

umn and form the back wall (Fig. 6.1).

, which are part of the vertebral col

coccyx

sacrum

, which form the lateral and anterior walls, and the

bones

The bony pelvis is composed of four bones: the two

and provides attachment for trunk and lower limb muscles.

tion, it contains, supports, and protects the pelvic viscera

the body from the vertebral column to the femurs. In addi

The bony pelvis’s main function is to transmit the weight of

continuous, the two regions are described separately.

abdomen. Although the abdominal and pelvic cavities are

is the region of the trunk that lies below the

The Pelvis

hip

and the

at the
the

and the

applied to the skeleton of the region—that is, the pelvic girdle or bony pelvis.

lower limbs meet. The word pelvis means “a basin” and is more correctly

*The term pelvis is loosely used to describe the region where the trunk and

242

CHAPTER 6

inflexible, they should be considered to form part of

the sacrotuberous ligaments are strong and relatively

(see page 246). From an obstetric standpoint, because

lesser sciatic foramina

and

greater

and 6.2) into the

(Figs. 6.1

sacrospinous ligaments

sacrotuberous

sciatic notches. The sciatic notches are divided by the

is between the ischiopubic rami, and laterally are the

outlet has three wide notches. Anteriorly, the pubic arch

(Figs. 6.2 and 6.3). The pelvic

pubic arch

riorly by the

the coccyx, laterally by the ischial tuberosities, and ante

(Fig. 6.2) is bounded posteriorly by

pelvic outlet

The

(Fig. 6.1).

opectineal lines, and anteriorly by the symphysis pubis

posteriorly by the sacral promontory, laterally by the ili

(Fig. 6.2), is bounded

pelvic brim

, or

pelvic inlet

The

lateral walls and an inferior wall or floor (Fig. 6.6).

parietal peritoneum. The pelvis has anterior, posterior, and

that are partly lined with muscles covered with fascia and

The walls of the pelvis are formed by bones and ligaments

Structure of the Pelvic Walls

a much deeper posterior wall (Fig. 6.2).

is a short, curved canal, with a shallow anterior wall and

lies between the inlet and the outlet. It

pelvic cavity

The

boundaries behind.

the sacrotuberous ligaments and the coccyx forming the

symphysis pubis forming the boundaries in front and

diamond shaped, with the ischiopubic rami and the

the perimeter of the pelvic outlet. Thus, the outlet is

The Pelvis: Part I—The Pelvic Walls

■

and

promontory of sacrum

first sacral spine

sacral canal

sacroiliac joint

lateral mass of sacrum

ischial spine

iliopectineal line

acetabulum

obturator foramen

ramus of ischium

pubic crest

pubic tubercle

body of pubis

superior ramus of pubis

sacrospinous ligament

sacrotuberous
ligament

tubercle of iliac crest

iliac fossa

iliopectineal line

pubic crest

pubic tubercle

symphysis pubis

tip of coccyx

greater trochanter of femur

promontory of sacrum

FIGURE 6.1

Anterior view of the male pelvis and female pelvis

(A)

(B).

Basic Anatomy

243

C L I N I C A L N O T E S

Clinical Concept: The Pelvis is a Basin with

, which is normally about 5 in. (13 cm).

diagonal conjugate

der of the symphysis. The fingers are then withdrawn and the

examining hand where it makes contact with the lower bor

the perineum sufficiently, an attempt is made to palpate the

amine its shape. Is it broad or angular? The examiner’s four

is an imaginary line joining the central

is the space between the inlet and the out

pelvic cavity

and posteriorly by the coccyx. The sacrotuberous ligaments

Four terms relating to areas of the pelvis are commonly used

importance in obstetrics. The female pelvis is well adapted for

pudendal nerve and internal pudendal vessels are the wires and

[lesser sciatic foramen]. In the case of the human body, the

get outside the building and then return through a second hole

floor, they have to pierce the wall [greater sciatic foramen] to

gain entrance to the apartment below, without going through the

vessels. (One can make a further analogy here: For the wires to

gluteal region for the pudendal nerve and the internal pudendal

sciatic foramen provides an entrance into the perineum from the

pudendal nerve, and the gluteal nerves and vessels; the lesser

the true pelvis into the gluteal region for the sciatic nerve, the

. The greater sciatic foramen provides an exit from

lesser sciatic

convert the greater

the passage of the anterior rami of the sacral spinal nerves. The

, for

The basin has many holes: The posterior wall has holes on the

inferior wall or floor formed by the important levator ani and coc

are partly lined with muscles (obturator internus and piriformis)

The walls of the pelvis are formed by bones and ligaments; these

Holes in its Walls

covered with fascia and parietal peritoneum. On the outside of

the pelvis are the attachments of the gluteal muscles and the

obturator externus muscle. The greater part of the bony pelvis is

thus sandwiched between inner and outer muscles.

The basin has anterior, posterior, and lateral walls and an

cygeus muscles and their covering fascia.

anterior surface of the sacrum, the anterior sacral foramina

sacrotuberous and sacrospinous ligaments

and lesser sciatic notches into the greater and
foramina

the levator ani and the coccygeus muscles are the floor.)

The lateral pelvic wall has a large hole, the obturator fora-

men, which is closed by the obturator membrane, except for a

small opening that permits the obturator nerve to leave the pelvis

and enter the thigh.

Pelvic Measurements in Obstetrics

The capacity and shape of the female pelvis are of fundamental

the process of childbirth. The pelvis is shallower and the bones

are smoother than in the male. The size of the pelvic inlet is simi-

lar in the two sexes, but in the female, the cavity is larger and

cylindrical and the pelvic outlet is wider in both the anteroposte-

rior and the transverse diameters.

in clinical practice:

■

The pelvic inlet or brim of the true pelvis (Fig. 6.4) is bounded

anteriorly by the symphysis pubis, laterally by the iliopectin-

eal lines, and posteriorly by the sacral promontory.

■

The pelvic outlet of the true pelvis (Fig. 6.4) is bounded in

front by the pubic arch, laterally by the ischial tuberosities,

also form part of the margin of the outlet.

■

The

let (Fig. 6.4).

■

The axis of the pelvis

points of the anteroposterior diameters from the inlet to the out-

let and is the curved course taken by the baby’s head as it de-

scends through the pelvis during childbirth (Figs. 6.4 and 6.5A).

Internal Pelvic Assessments
Internal pelvic assessments are made by vaginal examination

during the later weeks of pregnancy, when the pelvic tissues are

softer and more yielding than in the newly pregnant condition.

■

Pubic arch: Spread the fingers under the pubic arch and ex-

fingers should be able to rest comfortably in the angle below

the symphysis.

■

Lateral walls: Palpate the lateral walls and determine

whether they are concave, straight, or converging. The prom-

inence of the ischial spines and the position of the sacrospi-

nous ligaments are noted.

■

Posterior wall: The sacrum is palpated to determine whether

it is straight or well curved. Finally, if the patient has relaxed

promontory of the sacrum. The second finger of the examin-

ing hand is placed on the promontory, and the index finger of

the free hand, outside the vagina, is placed at the point on the

distance measured (Fig. 6.5B), providing the measurement of

the

The anteroposterior diameter from the sacrococcygeal joint

to the lower border of the symphysis is then estimated.

conditions such as malpresentation or malposition of the fetus,

the fetus. It may be indirectly responsible for dystocia by causing

labor). A contracted pelvis may obstruct the normal passage of

(difficult

The distance between the ischial tuber

Ischial tuberosities:

■

osities may be estimated by using the closed fist (Fig. 6.5D).

It measures about 4 in. (10 cm), but it is difficult to measure

exactly.

Needless to say, considerable clinical experience is required

to be able to assess the shape and size of the pelvis by vaginal

examination.

The Female Pelvis

Deformities of the pelvis may be responsible for dystocia

premature rupture of the fetal membranes, and uterine inertia.

The cause of pelvic deformities may be congenital (rare) or

acquired from disease, poor posture, or fractures caused by

injury. Pelvic deformities are more common in women who have

grown up in a poor environment and are undernourished. It is

probable that these women suffered in their youth from minor

degrees of rickets.

In 1933, Caldwell and Moloy classified pelves into four groups:

gynecoid, android, anthropoid, and platypelloid (Fig. 6.5C). The

type, present in about 24% of white females

gynecoid type, present in about 41% of women, is the typical

female pelvis, which was previously described.

The android type, present in about 33% of white females and

16% of black females, is the male or funnel-shaped pelvis with a

contracted outlet.

The anthropoid

and 41% of black females, is long, narrow, and oval shaped.

The platypelloid type, present in only about 2% of women,

is a wide pelvis flattened at the brim, with the promontory of the

sacrum pushed forward.

244

CHAPTER 6

symphysis pubis (Fig. 6.7).

by the bodies of the pubic bones, the pubic rami, and the

The anterior pelvic wall is the shallowest wall and is formed

Anterior Pelvic Wall

(Fig. 6.8).

rior and posterior rami of the upper four sacral nerves

sess on each side four foramina for the passage of the ante

The anterior and posterior surfaces of the sacrum pos

(Fig. 6.10).

down as far as the lower border of the 2nd sacral vertebra

It also contains the lower part of the subarachnoid space

spinal nerves; the filum terminale; and fibrofatty material.

rior and posterior roots of the lumbar, sacral, and coccygeal

sacral hiatus (Fig. 6.8). The sacral canal contains the ante

those of the 4th, fail to meet in the midline, forming the

The laminae of the 5th sacral vertebra, and sometimes

sacral canal

The vertebral foramina together form the

mark used when measuring the size of the pelvis.

(Fig. 6.2)—which is an important obstetric land

ontory

sacral prom

the posterior margin of the pelvic inlet—the

upper margins of the first sacral vertebra bulge forward as

(Fig. 6.1). The anterior and

sacroiliac joints

to form the

Laterally, the sacrum articulates with the two iliac bones

The narrow inferior border articulates with the coccyx.

base of the bone articulates with the fifth lumbar vertebra.

ward concavity (Figs. 6.2 and 6.8). The upper border or

together to form a single wedge-shaped bone with a for

The sacrum consists of five rudimentary vertebrae fused

Sacrum

(Fig. 6.9) and their covering of parietal pelvic fascia.

sacrum and coccyx (Fig. 6.8) and by the piriformis muscles

The posterior pelvic wall is extensive and is formed by the

Posterior Pelvic Wall

The Pelvis: Part I—The Pelvic Walls

-
-

iliac crest

rough surface for attachment of
interosseous ligament

posterior superior iliac spine

auricular surface

posterior inferior iliac spine

greater sciatic notch

ischial spine

lesser sciatic notch

obturator membrane

ischial tuberosity

ischial ramus

inferior ramus of pubis

obturator canal

pubic crest

pubic tubercle

body of pubis

iliopectineal line

anterior inferior
iliac spine

anterior superior
iliac spine

iliac fossa

ilium

tubercle
of ilium

acetabulum

obturator
foramen

pubis

ischium

line of fusion
of bones

superior ramus
of pubis

FIGURE 6.3

Right hip bone.

ilium, the ischium, and the pubis.

Lateral surface. Note the lines of fusion between the three bones—the

Medial surface.

promontory
of sacrum

pelvic inlet

body of pubis

pubic arch

pelvic outlet

ischial tuberosity

tip of coccyx

sacrospinous
ligament

sacrotuberous
ligament

FIGURE 6.2

Right half of the pelvis showing the pelvic inlet,

pelvic outlet, and sacrotuberous and sacrospinous ligaments.

Basic Anatomy

pubis. The obturator foramen is filled in by the obturator

, which is bounded by the parts of the ischium and

men

obturator fora

of the hip bone is a large opening, the

(Fig. 6.1). In the lower part

symphysis pubis

side at the

and articulates with the pubic bone of the opposite

cle

pubic tuber

pubic crest

of the pubis bears the

. The body

inferior pubic rami

superior

body

is the anterior part of the hip bone and has

The

(Fig. 6.3).

ity

ischial tuberos

ischial spine

bone and possesses an

is the inferior and posterior part of the hip

ischium

The

divide the false from the true pelvis.

ward around the inner surface of the ilium and serves to

runs downward and for

iliopectineal line

the sacrum. The

for articulation with

auricular surface

ilium is the large

posterior inferior iliac spines. On the inner surface of the

Below these spines are the corresponding anterior and

posterior superior iliac spines

anterior

between the

(Fig. 6.3). The iliac crest runs

iliac crest

bone, possesses the

, which is the upper flattened part of the hip

ilium

The

(Fig. 6.2).

sacrospinous ligaments

sacrotuberous

ence of the

by the pres

lesser sciatic foramina

greater

into the

. The sciatic notches are converted

spine of the ischium

by the

lesser sciatic notch

which is separated from the

greater sciatic notch

the acetabulum is a large notch, the

spherical head of the femur (Figs. 6.1 and 6.3). Behind

, which articulates with the hemi

acetabulum

sion, the

On the outer surface of the hip bone is a deep depres

symphysis pubis.

they also articulate with one another anteriorly at the

iliac joints and form the anterolateral walls of the pelvis;

The hip bones articulate with the sacrum at the sacro

bones fuse together to form one large, irregular bone.

. At puberty, these three

acetabulum

by cartilage at the

riorly (Fig. 6.3). The three separate bones are joined

inferiorly; and the pubis, which lies anteriorly and infe

lies superiorly; the ischium, which lies posteriorly and

In children, each hip bone consists of the ilium, which

internus muscle and its covering fascia.

rotuberous and sacrospinous ligaments, and the obturator

below the pelvic inlet, the obturator membrane, the sac

The lateral pelvic wall is formed by part of the hip bone

Lateral Pelvic Wall

245

Hip Bone

-
-

and

and an

pubis

and

and the

membrane (Fig. 6.3).

plexus.

It receives branches from the sacral

Nerve supply:

It is a lateral rotator of the femur at the hip joint.

Action:

greater trochanter of the femur.

men (Fig. 6.9). It is inserted into the upper border of the

region by passing laterally through the greater sciatic fora

mass of the sacrum and leaves the pelvis to enter the gluteal

The piriformis muscle arises from the front of the lateral

Piriformis Muscle

late with the sacral cornua (Fig. 6.8).

superior articular processes and project upward to articu

. The cornua are the remains of the pedicles and

cornua

transverse process

first vertebra possesses a rudimentary

The coccygeal vertebrae consist of bodies only, but the

with the lower end of the sacrum (Fig. 6.8).

form a small triangular bone, which articulates at its base

The coccyx consists of four vertebrae fused together to

lumbosacral angle

called the

so that it forms an angle with the fifth lumbar vertebra,

in the female than in the male. The sacrum is tilted forward

The sacrum is usually wider in proportion to its length

rior inferior iliac spine to the ischial tuberosity (Figs. 6.2

the lateral part of the sacrum and coccyx and the poste

The sacrotuberous ligament is strong and extends from

Sacrotuberous Ligament

(Fig. 6.3).

nerve and vessels as they leave the pelvis to enter the thigh

, for the passage of the obturator

obturator canal

gap, the

completely closes the obturator foramen, leaving a small

The obturator membrane is a fibrous sheet that almost

Obturator Membrane

and 6.9).

Coccyx

and

■

promontory

pelvic inlet

diagonal conjugate

axis of pelvis

pelvic outlet

Female

Male

pelvic inlet

pelvic outlet

pelvic cavity

pubic arch

FIGURE 6.4

Pelvic inlet, pelvic outlet, diagonal conjugate,

between the female and the male pelvis are also shown.

and axis of the pelvis. Some of the main differences

246

CHAPTER 6

lesser sciatic foramina

greater

and lesser sciatic notches into foramina, the

body (Fig. 6.11). The two ligaments also convert the greater

rotated upward at the sacroiliac joint by the weight of the

the lower end of the sacrum and the coccyx from being

The sacrotuberous and sacrospinous ligaments prevent

coccyx and by its apex to the spine of the ischium (Figs. 6.2

is attached by its base to the lateral part of the sacrum and

The sacrospinous ligament is strong and triangle shaped. It

Sacrospinous Ligament

branch from the sacral plexus

The nerve to the obturator internus, a

Nerve supply:

It laterally rotates the femur at the hip joint.

Action:

femur.

foramen and is inserted into the greater trochanter of the

tendon, which leaves the pelvis through the lesser sciatic

the hip bone (Fig. 6.12). The muscle fibers converge to a

face of the obturator membrane and the adjoining part of

The obturator internus muscle arises from the pelvic sur

Obturator Internus Muscle

The Pelvis: Part I—The Pelvic Walls

■

and 6.9).

and

axis of birth canal

measuring the diagonal conjugate

gynecoid

android

anthropoid

platypelloid

measuring transverse diameter of pelvic outlet

FIGURE 6.5

Estimation of the width of the pelvic outlet by

Different types of pelvic inlets, according to Caldwell and Moloy.

Procedure used in measuring the diagonal con

Birth canal. Interrupted line indicates the axis of the canal.

jugate. C.

means of a closed fist.

Basic Anatomy

covering the obturator internus, and the spine of the

tendinous arch formed by a thickening of the fascia

linear origin from the back of the body of the pubis, a

The levator ani muscle is a wide thin sheet that has a

Levator Ani Muscle

247

ischium (Fig.

om this extensive origin, groups of

6.13). Fr

fibers sweep downward and medially to their insertion
(Fig.

ws:

6.14) as follo

the perineal body.

The sphincter vaginae constrict the vagina and stabilize

tae support the prostate and stabilize the perineal body.

, in front of the anal canal. The levator prosta

ineal body

per

are inserted into a mass of fibrous tissue, called the

form a sling around the prostate or vagina and

vaginae

sphincter

levator prostatae

The

Anterior fibers:

-
-

vagina in females.

passage of the urethra in males and the urethra and the

ering fasciae (Fig. 6.13). It is incomplete anteriorly to allow

ani muscles and the small coccygeus muscles and their cov

The pelvic diaphragm is formed by the important levatores

ered in detail in Chapter 8.

viscera, and the perineum below. The perineum is consid

into the main pelvic cavity above, which contains the pelvic

The pelvic floor stretches across the pelvis and divides it

formed by the pelvic diaphragm.

The floor of the pelvis supports the pelvic viscera and is

Inferior Pelvic Wall or Pelvic Floor

, between the tip of the coccyx and the anal

cygeal body

anococ

inserted into a small fibrous mass, called the

passes posteriorly to be

pubococcygeus

canal. The

sling around the junction of the rectum and anal

forms a

puborectalis

The

Intermediate fibers:

canal.

Pelvic Diaphragm

pelvic inlet

anterior wall

pelvic outlet

inferior wall or floor

posterior wall

FIGURE 6.6

Right half of the pelvis showing the pelvic walls.

body of pubis

superior ramus of pubis

obturator
membrane

inferior ramus of pubis

symphysis pubis

FIGURE 6.7

Anterior wall of the pelvis (posterior view).

superior articular
process

promontory

lateral mass

anterior sacral
foramina

transverse process
of coccyx

sacral canal

superior articular
process

first sacral spine

auricular surface

posterior sacral
foramina

sacral hiatus

tip of coccyx

coccygeal cornu

median crest

sacral cornu

FIGURE 6.8

Sacrum.

Posterior view.

Anterior view.

248

CHAPTER 6

visceral layers.

neum. The pelvic fascia can be divided into parietal and

Below, the fascia is continuous with the fascia of the peri

tinuous above with the fascia lining the abdominal walls.

The pelvic fascia is formed of connective tissue and is con

in Table 6.1.

walls and floor, their nerve supply, and their action is given

A summary of the attachments of the muscles of the pelvic

A branch of the 4th and 5th sacral nerves

Nerve supply:

porting the pelvic viscera.

The two muscles assist the levatores ani in sup

Action:

and into the coccyx (Figs. 6.13 and 6.14).

ischium and is inserted into the lower end of the sacrum

This small triangular muscle arises from the spine of the

Coccygeus Muscle

pudendal nerve

sacral nerve and from the perineal branch of the

The perineal branch of the fourth

Nerve supply:

vagina.

in the female they serve also as a sphincter of the

sphincter action on the anorectal junction, and

occurs in coughing). They also have an important

and expulsive efforts of the abdominal muscles (as

the rise in intrapelvic pressure during the straining

The Pelvis: Part I—The Pelvic Walls

■

Pelvic Fascia

maintains the pelvic viscera in position. They resist

form an efficient muscular sling that supports and

The levatores ani muscles of the two sides

Action:

anococcygeal body and the coccyx.

is inserted into the

iliococcygeus

The

Posterior fibers:

■

sacral canal

lumbosacral trunk

sciatic nerve

symphysis pubis

sacrospinous ligament

sacrotuberous ligament

greater sciatic foramen

acetabulum

pudendal nerve

piriformis muscle

FIGURE 6.9

Posterior wall of the pelvis.

sacral canal

lumbosacral trunk

sciatic nerve

symphysis pubis

sacrospinous ligament

sacrotuberous ligament

greater sciatic foramen

acetabulum

pudendal nerve

piriformis muscle

FIGURE 6.9

Posterior wall of the pelvis.

filum terminale

cauda equina

dura mater

nerve roots of
sacral nerves

posterior
root ganglia

cut laminae
of sacrum

filum terminale

posterior

superior

iliac spine

FIGURE 6.10

Sacrum from behind. Laminae have been

vertebra.

below, at the level of the lower border of the 1st lumbar

removed to show the sacral nerve roots lying within the

sacral canal. Note that in the adult the spinal cord ends

Basic Anatomy

249

posterior sacroiliac

ligament

ilium

sacrum

joint cavity

sacrotuberous
ligament

greater sciatic
foramen

sacrospinous
ligament

lesser sciatic foramen

anterior and posterior
symphyseal ligaments

symphysis pubis

disc of fibrocartilage

body of pubis

anterior sacroiliac
ligament

plates of hyaline
cartilage

sacroiliac joint

interosseous sacroiliac
ligament

weight of trunk

axis of rotation

sacrotuberous and
sacrospinous ligaments

plates of hyaline
cartilage

FIGURE 6.11

Horizontal section through the pelvis showing the sacroiliac joints and the symphysis pubis. The lower diagram

the weight of the trunk.

shows the function of the sacrotuberous and sacrospinous ligaments in resisting the rotation force exerted on the sacrum by

internal iliac artery
and vein

lateral sacral artery

middle rectal artery

internal
pudendal artery

sciatic nerve

pudendal nerve

inferior gluteal artery

sacrotuberous ligament

obturator internus muscle

obturator nerve and vessels

common iliac artery and vein

ureter

lumbosacral trunk

external iliac artery

external iliac vein

deep circumflex iliac artery

inferior epigastric artery

obliterated umbilical artery

superior vesical artery

FIGURE 6.12

Lateral wall of the pelvis.

250

CHAPTER 6

The Pelvis: Part I—The Pelvic Walls

sacrotuberous ligament

ischial spine

coccyx

coccygeus muscle

levator ani muscle

obturator internus muscle

obturator canal

linear thickening of fascia

covering obturator internus muscle

FIGURE 6.13

Inferior wall or floor of the pelvis.

symphysis pubis

levator prostatae or
sphincter vaginae

puborectalis

iliococcygeus

perineal body

coccygeus

tip of coccyx

anococcygeal body

junction of rectum
and anal canal

pubococcygeus

FIGURE 6.14

Levator ani muscle and coccygeus muscle seen on their inferior aspects. Note that the levator ani is made up

muscular floor to the pelvis, known as the pelvic diaphragm.

of several different muscle groups. The levator ani and coccygeus muscles with their fascial coverings form a continuous

252

CHAPTER 6

see pages 278 and 296.

with the visceral peritoneum (Fig. 6.17). For further details,

reflected onto the pelvic viscera and becomes continuous

The parietal peritoneum lines the pelvic walls and is

sacrocervical ligaments.

to their attachments, for example, the pubovesical and the

vides support. These fascial ligaments are named according

and extends from the viscus to the pelvic walls and pro

the pelvic viscera. In certain locations, the fascia thickens

The visceral layer of pelvic fascia covers and supports all

Visceral Layer of Pelvic Fascia

superior fascial layer of the urogenital diaphragm.

and the perineal membrane (see page 314) and forms the

in the perineum. It covers the sphincter urethrae muscle

fascia covering the inferior surface of the pelvic diaphragm,

vic fascia becomes continuous through the opening with the

the pelvic diaphragm is deficient anteriorly, the parietal pel

named according to the muscle it overlies (Fig. 6.17). Where

The parietal pelvic fascia lines the walls of the pelvis and is

The Pelvis: Part I—The Pelvic Walls

Parietal Pelvic Fascia

Pelvic Peritoneum

Injury to the Pelvic Floor

may

. In the latter condition, the

and alteration in the position of the bladder neck and urethra,

, herniation of the bladder

vaginal prolapse

Injury to the pelvic floor during a difficult childbirth can result

in the loss of support for the pelvic viscera leading to uterine

and

(cystocele),

leading to stress incontinence

patient dribbles urine whenever the intra-abdominal pres-

sure is raised, as in coughing. Prolapse of the rectum

also occur.

Partial Fusion of the Sacral Vertebrae

The 1st sacral vertebra can be partly or completely separated

from the 2nd sacral vertebra. Occasionally, on radiographs of

the vertebral column, examples are seen in which the 5th lumbar

vertebra has fused with the 1st sacral vertebra.

Trauma to the True Pelvis

Trauma to the true pelvis can result in fracture of the lateral

mass of the sacrum (see previous column).

Name of Muscle

Origin

Insertion

Nerve Supply

Action

Piriformis

Front of sacrum

Greater trochanter of femur

Sacral plexus

Lateral rotator of femur

at hip joint

Obturator internus

Obturator membrane and

adjoining part of hip bone

Greater trochanter of femur

Nerve to obturator

internus from

sacral plexus

Lateral rotator of femur

at hip joint

Levator ani

Body of pubis, fascia of

obturator internus, spine

of ischium

Perineal body;

anococcygeal body;

walls of prostate, vagina,

rectum, and anal canal

Fourth sacral nerve,

pudendal nerve

Supports pelvic

viscera; sphincter to

anorectal junction

and vagina

Coccygeus

Spine of ischium

Lower end of sacrum;

coccyx

Fourth and fifth sacral

nerve

Assists levator ani

to support pelvic

viscera; flexes

coccyx

Muscles of the Pelvic Walls and Floor

T A B L E 6 . 1

anterior superior
iliac spine

ischial tuberosity

anterior
inferior
iliac
spine

FIGURE 6.15

hamstring muscles, for the avulsion of the ischial tuberosity.

for the avulsion of the anterior inferior iliac spine; and the

iliac spine; the straight head of the rectus femoris muscle,

cle is responsible for the avulsion of the anterior superior

Avulsion fractures of the pelvis. The sartorius mus

Different types of fractures of the pelvic

A–C.

basin. D.